Method and device for bonding substrates

ABSTRACT

A method for bonding a first substrate with a second substrate, with the following sequence: production of a first amorphous layer on the first substrate and/or production of a second amorphous layer on the second substrate, bonding of the first substrate with the second substrate at the amorphous layer or at the amorphous layers to form a substrate stack, irradiation of the amorphous layer or the amorphous layers with radiation in such a way that the amorphous layer or the amorphous layers is/are transformed into a crystalline layer or crystalline layers.

RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.16/481,994, filed Jul. 30, 2019, which is a U.S. National StageApplication of International Application No. PCT/EP2017/053918, filedFeb. 21, 2017, said patent applications hereby fully incorporated hereinby reference.

FIELD OF THE INVENTION

The present invention relates to a method and a device for bondingsubstrates as well as a substrate stack according to the claims.

BACKGROUND OF THE INVENTION

In the semiconductor industry, different bonding technologies havealready been used for a number of years to join substrates together. Thejoining process is referred to as bonding. A distinction is made inparticular between the temporary bonding methods and the permanentbonding methods.

In the case of the temporary bonding methods, a product substrate isbonded in particular with a carrier substrate in such a way that it canbe detached again after processing. It is possible with the aid of thetemporary bonding process to stabilize the product substratemechanically. The mechanical stabilization guarantees that the productsubstrate can be handled without becoming arched, deformed or breaking.Stabilizations by the carrier substrates are primarily required duringand after a back-thinning process. A back-thinning process permits thereduction of the product substrate thickness to several microns.

In the case of permanent bonding methods, at least two substrates arebonded together durably, permanently. The permanent bonding of twosubstrates also permits the production of multi-layer structures. Thesemulti-layer structures can be comprised of the same or of differentmaterials.

The permanent bonding method of anodic bonding is used for bondingion-containing substrates permanently together. In most cases, one ofthe two substrates is a glass substrate.

A further permanent bonding method is metal bonding. In the case ofmetal bonding, an alloy is provided between the substrates to be bondedor a homo-atomic bonding i.e. comprising only one type of atom, takesplace. The liquid phase solidifies in an optional solidification processand forms the bonding layer between the two substrates. Bonding withoutthe formation of a molten phase is also conceivable.

A further permanent bonding method is fusion bonding, also referred toas direct bonding. In the case of fusion bonding, two plane, puresubstrate surfaces are bonded together by contacting. The bondingprocess is split up into two steps. In a first step, contacting of thetwo substrates takes place. The fixing of the two substrates mainlytakes place by van der Waals forces. The fixing is referred to as aprebond. These forces allow a fixing to be produced which is strongenough to bond the substrates together so firmly that a mutualdisplacement, in particular due to the application of a shear force, isnow only possible with considerable expenditure of force. On the otherhand, the two substrates can be separated again from one anotherrelatively easily, in particular by the application of a normal force.Normal forces preferably engage at the edge, in order to bring about awedge effect in the interface between the two substrates that generatesa running crack and thus separates the two substrates from one anotheragain. In order to produce a permanent fusion bond, the substrate stackundergoes a heat treatment, also referred to as annealing. The heattreatment leads to the formation of covalent bonds between the surfacesof the two substrates. A permanent bond produced in this way is now onlydetachable by the use of a correspondingly high force, in most casesinvolving destruction of the substrates.

The heat treatment required to produce the bonding strength alsopresents technical challenges. The bonded substrates have often alreadybeen provided with functional units such as for example microchips,MEMs, sensors, LEDs, which have a temperature sensitivity. Microchips inparticular have a relatively high degree of doping. At raisedtemperatures, the doping elements have an increased diffusion capacity,which can lead to an undesired, disadvantageous distribution of thedoping in the substrate. Furthermore, heat treatments are alwaysassociated with raised temperatures and therefore also with increasedcosts, with the creation of thermal stresses, thermally induceddisplacements and with longer process times for the heating and cooling.Bonding should therefore take place at the lowest possible temperatures.

Further methods for direct bonding represent surface-activated directbonds. The surface energy of the bond is increased with the aid of asurface activation of at least one of the substrates, so that bondstrengths that are comparable with the strength of the substratematerial arise at room temperature.

Various approaches to surface activation aid in reduction of the heattreatment temperature and/or duration. A plasma treatment or an ion beamtreatment can be used for the treatment of the surfaces to be bonded.Empirically, most, if not even all, surface activation methods areaccompanied by an amorphization of the surfaces to be bonded.

A plasma treatment for the cleaning and activation of a substratesurface would be one option for bonding at relatively low temperatures.Such plasma methods, however, do not work, or only work with greatdifficulty, in the case of surfaces with a high affinity for oxygen, inparticular with metal surfaces. Metals with a high affinity for oxygenoxidize and generally form relatively stable oxides. The oxides are inturn a hindrance to the bonding process. Such oxidized metals can alsobe relatively difficult to bond together by diffusion bonds. On theother hand, the bonding of plasma-activated, in particularmonocrystalline silicon, which forms a silicon dioxide layer, works verywell. The silicon dioxide layer is eminently well suited for bonding.These negative effects of the oxides therefore do not necessarily relateto all material classes.

Publication U.S. Pat. No. 5,441,776 describes a method for bonding afirst electrode to a hydrogenated, amorphous silicon layer. Thisamorphous silicon layer is deposited on the surface of a substrate bydeposition processes.

Publication U.S. Pat. No. 7,462,552B2 shows a method in which a chemicalvapor deposition (CVD) is used, in order to deposit an amorphous siliconlayer on the surface of a substrate. The amorphous layer has a thicknessbetween 0.5 and 10 μm.

There are several approaches in the literature that described directbonding at lower temperature. An approach in PCT/EP2013/064239 includesthe application of a sacrificial layer, which is dissolved in thesubstrate material during and/or after the bonding process. A furtherapproach in PCT/EP2011/064874 describes the production of a permanentbond by phase transformations. The mentioned publications relate inparticular to metal surfaces, which are more likely bonded by means ofmetal bonding and not by means of covalent bonds. In PCT/EP2014/056545,an optimized direct bonding method of silicon by surface cleaning isdescribed.

A further approach is represented by WO2015197112A1, in which many ofthe drawbacks of the mentioned technologies are reduced. Thus, thebonding layer is kept to a thickness of several 10 nm, so that theoptical properties of the stack in particular are influenced onlyslightly.

A kind of weld joint is represented by publications US20130112650A1 andUS20140230990A1, wherein metal layers are deposited on the surfaces tobe bonded, which metal layers are locally melted by means of laser beam.At least linear bonds thus arise, with which the substrates can bebonded.

All the mentioned methods and bonding devices produce a bonded substratestack after a jointing process. However, either additional materialssuch as metals and/or their ions are used in all the methods or oxidesand/or nitrides of the substrates are formed and bonded together.

SUMMARY OF THE INVENTION

A problem to be solved by the present invention is to remove thedrawbacks of the prior art and in particular to achieve a better bondingresult.

This problem is solved with the subject matter of the claims.Advantageous developments of the invention are stated in the sub-claims.All combinations of at least two of the features stated in thedescription, the claims and/or the drawings also fall within the scopeof the invention. In the case of value ranges, values also lying withinthe stated limits are also intended to be disclosed as limiting valuesand can be claimed in any combination.

According to the invention, a method for bonding a first substrate witha second substrate is provided, with the following sequence:

production of a first amorphous layer on the first substrate and/orproduction of a second amorphous layer on the second substrate,

bonding of the first substrate with the second substrate at theamorphous layer or at the amorphous layers to form a substrate stack,

irradiation of the amorphous layer or the amorphous layers withradiation in such a way that the amorphous layer or the amorphous layersis/are transformed into a crystalline layer or crystalline layers.

Also, according to the invention, a device for bonding a first substratewith a second substrate is provided, in particular using a methodaccording to the invention, comprising:

a receiving means for receiving the substrates,

a bonding device for bonding the substrates,

an irradiation device,

wherein the device is constituted in such a way that a first amorphouslayer can be produced on the first substrate and/or a second amorphouslayer can be produced on the second substrate, that the first substratecan be bonded with the second substrate at the amorphous layer or at theamorphous layers for the formation of a substrate stack, that theamorphous layer or the amorphous layers can be irradiated with radiationby means of the irradiation device, in such a way that the amorphouslayer or the amorphous layers can be transformed into a crystallinelayer or crystalline layers.

Also according to the invention, a substrate stack is provided, whichhas been bonded using a device according to the invention and/or amethod according to the invention.

According to the invention, two individual substrates can be bondedtogether. A substrate can however also be bonded with a substrate stackor two substrate stacks can be bonded together. A substrate stackcomprises two or more bonded substrates.

A substrate or substrate stack to be bonded can have an amorphous layeron one side only or can have an amorphous layer on both sides.

For the purpose of simplification, substrate is always intended in thefollowing to mean both a single substrate as well as a substrate stack,unless anything is stated to the contrary.

A basic idea of the invention consists in the fact that good prefixing(prebonding) of the substrates is produced by the at least one amorphouslayer and a substrate stack bonded largely transition-free is producedby the transformation of the amorphous layer(s). According to theinvention, the generated heat is relatively small with the correctselection of the laser wavelength and is limited locally to theamorphous layer(s). Stresses in the substrate stack can thus besignificantly reduced. In addition, the process times are comparativelyshort.

The at least one amorphous layer is produced at least on a partialregion of the substrate surface, so that a sufficiently strong prebondcan be achieved. The at least one amorphous layer is preferably producedon the entire substrate surface, so that a prebond with maximum strengthcan be achieved. It is however also conceivable for the amorphous layerto be produced only in partial regions of the substrate surface, inparticular in the case of the conducting surface regions of a hybridbond.

During the irradiation of the amorphous layer(s), bonds of thesubstrates arising in particular due to the van der Waals forces aretransformed into firm, in particular atomic, bonds, in particular intocovalent bonds, and defects present are closed.

According to the invention, at least one of the substrates is coveredwith an amorphous layer. If only one of the substrates is covered withan amorphous layer and the other substrate is not covered with amorphouslayer, the substrates are bonded together at the amorphous layer.

An amorphous layer is preferably produced on both substrates and thesubstrates are bonded together at the amorphous layers. A particularlyfirm prebond can advantageously thus be produced.

At least one of the substrates is preferably a crystalline substrate,particularly preferably a monocrystalline substrate. Very particularlypreferably, both substrates are crystalline substrates, more preferablymonocrystalline substrates. Advantageously, the radiation can thus reachthe amorphous layer(s) largely undisrupted, so that heating of thesubstrates is minimized, as a result of which stresses in the substratestack are minimized. It is also conceivable for the substrates to bepolycrystalline, in particular even nanocrystalline. Especially in thecase of hybrid bonds, known to the person skilled in the art, theelectrically conductive regions to be bonded together are preferablypolycrystalline, in particular comprising polycrystalline copper. Insuch cases, the method according to the invention can also be used onlyon partial regions of a substrate, if need be, and does not necessarilyhave to take place over the entire area of the substrate. The full-areaamorphization of all the dielectric and electrical regions of a hybridsurface is however particularly preferable, especially because thehybrid surface can be amorphized at the same time.

According to the invention, the at least one amorphous layer istransformed at least in regions into a crystalline layer, so that alargely transition-free substrate stack is produced. The at least oneamorphous layer is preferably transformed predominantly into acrystalline layer, very particularly preferably completely. An almostcompletely transition-free or a completely transition-free substratestack can thus advantageously be produced.

According to the invention, the amorphous layer is produced at least ona partial region of the surface (also referred to below as the bondingsurface) of the substrate/substrates to be bonded. An amorphous layer ispreferably produced on the predominant part of the bonding surface ofthe substrate/substrates. Particularly preferably, an amorphous layer isproduced on the entire bonding surface of the substrate/substrates. Aparticularly firm prebond can thus advantageously be produced and alargely or completely transition-free substrate stack can be produced.

Furthermore, provision is made such that the crystalline phase of thefirst and/or the second substrate is at least 50%, preferably at least70%, still more preferably at least 90%, most preferably at least 95%,with utmost preference at least 99% transparent for the employedradiation of a radiation source. The radiation can thus reach theamorphous layer(s) largely unhindered, so that a transformation of theamorphous layer(s) through the substrate is possible. The entireamorphous layer or layers can thus advantageously be reached by theradiation. In addition, the radiation source of the radiation canadvantageously be arranged on the rear side of the substrates. The rearside is the side of the substrate that is facing away from the bondingsurface.

According to the invention, the at least one amorphous layer at leastpartially absorbs the radiation. More than 50% of the radiant energy ofthe radiation is preferably absorbed, more preferably more than 70%,particularly preferably more than 80%, very particularly preferably morethan 90%. A particularly efficient transformation into the crystallinephase can thus advantageously take place.

The radiation is preferably laser radiation. This is focused on the atleast one amorphous layer and thus acts only on the at least oneamorphous layer. The thermal load on the substrate stack and thereforethe induced mechanical stresses are thus advantageously reduced.

Furthermore, provision is preferably made such that the radiationstrikes the amorphous layer(s) at right angles, which include anydeviation of less than ±5 degrees, preferably less than ±3 degrees,particularly preferably less than ±1 degree from the normal. Theradiation can thus be absorbed in the optimum manner by the at least oneamorphous layer, so that a particularly efficient transformation intothe crystalline phase can be achieved. In addition, the irradiation cantake place from the rear side of the substrate or the substrates,because of which the entire amorphous layer or the entire amorphouslayers can be reached by the radiation. In addition, the arrangement ofthe radiation source(s) and the substrates can be simplified, sinceirradiation from the side is not necessary.

Furthermore, provision is preferably made such that the radiation isgenerated by a broadband emitter, which emits in the energy rangebetween 1 eV and 10E6 eV, preferably between 1 eV and 10E3 eV, stillmore preferably between 1 eV and 10 eV, most preferably between 1 eV and3 eV. Advantageously, the radiation in these energy ranges is passedthrough the substrate or the substrates largely unhindered and isabsorbed by the amorphous layer(s), so that the transformation into thecrystalline phase can take place. The entire amorphous layer or theentire amorphous layers can thus be reached and irradiation from therear side of the substrate or the substrates can take place.

Furthermore, provision is preferably made such that the radiant power ofthe radiation lies between 0.01 Watt and 10000 Watt, preferably between0.1 Watt and 1000 Watt, most preferably between 1 Watt and 100 Watt. Inthese power ranges, the at least one amorphous layer can be brought tothe optimum temperature, so that the transformation into the crystallinephase can take place.

Furthermore, provision is preferably made such that temperatures of over200° C. are produced by the radiation in the amorphous layer(s),preferably over 400° C., particularly preferably over 600° C., stillmore preferably over 800° C., most preferably over 1200° C. Aparticularly efficient transformation into the crystalline phase canadvantageously take place in these temperature ranges.

Furthermore, provision is preferably made such that the irradiation timeon a point lies below 30 s, preferably below 15 s, particularlypreferably below 1 s, and very particularly preferably below 100 ms. Atransformation into the crystalline phase can be achieved in these timeranges, so that a considerable reduction in process times can beachieved, since only the amorphous layer(s) are irradiated.

Furthermore, provision is preferably made such that a reflection of theradiation at the substrates surfaces and/or substrate stack surfacesamounts to less than 4% of an output intensity of a radiation source,preferably less than 3%, particularly preferably less than 1%. Theenergy loss when the radiation enters into the substrate(s) is thusminimized, so that the maximum energy for the transformation of theamorphous layer(s) into the crystalline phase can be used.

In particular, at least one antireflection layer and/or at least onemoth-eye structure is deposited on the side(s) of the substrate or thesubstrates that lies/lie opposite the bonding surface(s), wherein aliquid and/or a liquid film is in particular arranged between theradiation source and the substrate surface.

The transmission, the ratio between the intensity at the surface atwhich the radiation enters and the residual intensity at the amorphousbonding interface according to the invention depends according to theLambert-Beer law on the length of the transmission path through thematerial and the absorption coefficient of the material. The latter is afunction of the wavelength. The stated percentage transmission valuestherefore preferably apply to all material/thickness/wavelengthcombinations, in the sense that according to the invention atransmission as high as possible through the crystalline phase of thegiven material used with a given thickness and wavelength is sought.

The energy loss when the radiation passes through the substrate(s) isthus minimized, so that the maximum energy for the transformation of theamorphous layer(s) into the crystalline phase can be used.

A fluctuation of the transparency depending on a wavelength of theradiation lies here below 10%, preferably below 5%, particularlypreferably below 3%, very particularly preferably below 1%.

Furthermore, provision is preferably made such that, before and/orduring the irradiation, heating of at least one of the substrates,preferably of both substrates, takes place, wherein the substrate(s) areheated above 25° C., preferably above 150° C., particularly preferablyabove 300° C. The transformation of the at least one amorphous layerinto the crystalline phase can be advantageously assisted andfacilitated by the heating.

Furthermore, provision is preferably made such that the amorphouslayer(s) is/are produced by amorphisation processes, in particular ionbeam processes and/or plasma processes, wherein particles striking thesubstrate or the substrates have energies between 0.01 eV and 1000 eV,preferably between 0.1 eV and 100 eV, still more preferably between 1 eVand 10 eV.

The penetration depth of the particles into the substrate is greaterthan 0 nm, preferably greater than 5 nm, still more preferably greaterthan 10 nm, most preferably greater than 25 nm, with utmost preferencegreater than 50 nm.

The thickness(es) of the amorphous layer(s) is/are preferably less than50 nm, preferably less than 20 nm, particularly preferably less than 10nm, very particularly preferably less than 5 nm, in the optimum caseless than 2 nm, in the ideal case less than 1 nm. A transition-freesubstrate stack can thus advantageously be created.

The variation in the thickness(es) of the amorphous layer(s) ispreferably less than 20 times the lattice constant of the substratecrystals, preferably less than 10 times the lattice constant of thesubstrate crystal, particularly preferably less than 5 times the latticeconstant of the substrate crystal. A uniform amorphous layer can thusadvantageously be produced, as a result of which the crystallization isfacilitated and a transition-free substrate stack can be created.

The first substrate and/or the second substrate is preferably freed atleast partially from a natural oxide layer before the amorphous layer(s)is/are produced. Interfering influences of oxides are thus removed. Thecrystallization can thus be facilitated and a transition-free substratestack created.

The amorphous layer(s) is/are preferably produced by the followingmethods:

chemical vapor deposition (CVD),

physical vapor deposition (PVD),

plasma treatment, or

ion beam treatment.

In a very preferred embodiment according to the invention, an existingcrystalline substrate surface is amorphized, in particular by ionbombardment. It is however feasible, but less preferable, for anamorphous layer to be deposited on an existing crystalline substratesurface.

A basic idea of the invention is in particular that the differences inthe absorption of different phases of a substrate are utilized primarilyto heat the bonding interface. At least one substrate can becrystalline, in particular monocrystalline. At least one of thesubstrates should comprise an amorphous layer.

The, in particular crystalline, substrate or the, in particularcrystalline, substrates should have a low absorption, a hightransmission and a low reflection for the radiation. The amorphous layerhas, in return, a high absorption, a low transmission and low reflectionfor the radiation. The radiation is thus converted chiefly in thebonding interface (i.e. at the bonding interfaces).

A large part of the radiation is absorbed in the amorphous layer or theamorphous layers and converted into heat, so that an increased thermalmotion of the atoms in the amorphous layer or the amorphous layers leadsto a rearrangement of the atoms. In particular, a phase transformationof the amorphous phase or phases into the crystalline phase or phasestakes place at the bonding interface.

A substrate stack with a relatively perfect, in particularmonocrystalline, lattice can thus be produced. The lattice thus arisingmay in fact still exhibit dislocations, which however do notsignificantly impair the achieved result.

The idea according to the invention consists in particular in the factthat a substrate stack bonded with a prebond is treated locally by meansof radiation, in such a way that the amorphous state of the bondinginterface and its surroundings are transformed into the crystallinestate. The bond strength is also increased by the disappearance of theamorphous bonding interface between the two substrates. In particular,the electrical properties of the bonding interface are also improved bythe extensive transformation into the crystalline phase. For example, apredominantly ohmic transition can thus preferably be guaranteed. Thismeans for example that a threshold voltage/breakdown voltage of a diodeportion makes up less than 10% of the total voltage drop at thetransition.

The simplification of the methods for bonding is advantageous for theinvention. By means of suitable material pairings and material use ofthe substrate, a bond can arise without foreign-atom or foreign-ionloading. Homogeneous perfect crystals, at most except for severallattice defects, in particular vacancies and dislocations, are bondedtogether, so that the electrical properties are further optimized andimproved.

The present invention uses, in particular electromagnetic, radiation totransform the amorphous bonding interface of the substrate stack bymeans of phase transformation into the crystalline phase and thus tobond the substrates of the substrate stack inseparably together.

The method according to the invention preferably uses the followingprocess steps, which can be carried out in any sequence:

production of an amorphized layer on the substrate surfaces to bebonded,

cleaning of the substrates surfaces,

alignment of the substrates with one another,

prebond by means of direct bonding,

laser treatment accorded to the invention to remove the bondinginterface.

Different phases exhibit a very different absorption capacity inspecific energy ranges or wavelength ranges.

At specific wavelengths and/or wavelength ranges, crystalline phases ofsubstrate materials have a high degree of transmission, a low degree ofabsorption and a low degree of reflection. Radiation can thus passthrough the crystalline phase virtually unhindered.

At the same specific wavelengths and/or wavelength ranges, amorphousphases of substrate materials have a low degree of transmission, a highdegree of absorption and a low degree of reflection. The radiation isthus absorbed predominantly by the amorphous phase.

The absorption of the radiation leads to a, in particular local,targeted heating of the amorphous phase. Heating is identical to anincrease in the energy content or to an increase in the thermal motion.According to the invention, it is possible to achieve a thermal motionstate in the amorphous phase that is so high that a phasetransformation, in particular crystallization, occurs.

According to the invention, the amorphous phase will be rearrangedduring and/or after the heating input and subsequently crystallize as aresult thereof. According to the invention, this phase transformationtakes place in the amorphous phase of the bonding interface. The effectof the energy input is that the system is brought over a thresholdenergy that is required to enable crystallization. The total energy ofthe crystalline system, however, is less than that of the amorphoussystem. The system thus tends towards the crystalline structure.

A local phase transformation, in particular crystallization of thebonding interface, thus leads to healing of the bonding interface.

The present invention controls or regulates the necessary physicaleffects and boundary conditions by means of parameter sets orformulations, wherein formulations are optimized value collections ofparameters, which are connected in functional or process terms. The useof formulations permits the reproducibility of processes. These include:

Material: substrate geometry with shape and position tolerancesaccording to semi-standards and other specifications, evenness andwaviness of the substrates, substrate material, doping, amorphization,layer thickness of the amorphous layer,

Material pairing: if substrates with the same amorphous layer, butdifferent material in the substrate volume (bulk) are bonded, or if thesubstrates are virtually identical to one another.

Substrate preparation: cleanliness of substrates, foreign atom load,interstratification of atomic water layers or gases on the surfaces tobe bonded and in the interlayers.

Radiation input of the radiation with wavelength, duration of action,angle of incidence.

Ambient conditions for the substrate stack: temperature, atmosphere.

The substrates can have any arbitrary shape, but are preferably round.The diameter of the substrates is in particular standardizedindustrially. For wafers, the industry-standard diameters are 1 inch, 2inch, 3 inch, 4 inch, 5 inch, 6 inch, 8 inch, 12 inch and 18 inch. Theembodiment according to the invention, however, can handle any substrateirrespective of its diameter. Non-round substrates (in particularrectangular panels, wafer fragments) are also intended to be handled.

Subsequently, evenness will be used as a measure of the perfection of aplanar face, in particular a surface. Deviations from a planar surfacearise due to waviness and roughness. The waviness of a surface ischaracterized by a certain periodic elevation and depression of thesurface, in particular in the millimeter range, less often in the micronrange. Roughness, on the other hand, is more of an aperiodic phenomenonin the micrometer or nanometer range. The precise definition of suchsurface properties is known to every expert in surface physics,tribology, mechanical engineering or materials sciences.

The substrate surface and its deviation from a mathematical plane can beregarded as a superimposition of waviness and roughness. According tothe invention, it is advantageous that the surfaces to be bonded have aminimum deviation from the perfect, mathematical plane. In order to dealwith the various deviations from the ideal surface, the term roughnesswill be used synonymously for the superimposition of all such effects inthe remaining part of the patent specification. The roughness isindicated either as a mean roughness, a quadratic roughness or as anaveraged roughness depth. The ascertained values for the mean roughness,the quadratic roughness and the averaged roughness depth generallydiffer for the same measurement section or measurement area, but lie inthe same range of order of magnitude. Consequently, the followingnumerical value ranges for the roughness are to be understood either asvalues of the mean roughness, the quadratic roughness or of the averagedroughness depth. The roughness is less than 100 nm, preferably less than10 nm, more preferably less than 5 nm, most preferably less than 3 nm,with utmost preference less than 2 nm.

Substrate materials can be both wafers available in the trade, i.e.element semiconductors, compound semiconductors and organicsemiconductors.

Here, however, use is chiefly made of semiconductors, which containelements such as silicon, and/or germanium, and/or carbon and/ortellurium and/or aluminum and/or indium and/or gallium, in particular asmain components.

Apart from the substrate material, which in particular should be astransparent as possible for the radiation used, other materials can beused in order to influence the physical properties of the substratematerial.

Insofar as the materials are dissolved in the substrate material, itinvolves a solution in the ppm (parts per million) range, also referredto as doping.

Doping influences the electronic and electromagnetic properties of thesubstrates. Accordingly, doping has an influence on the substratematerial, its transparency and its absorption. Furthermore, it isconceivable to produce corresponding predetermined breaking points inthe substrate with the aid of doping.

Amorphization is a phase transformation of an ordered crystal into anamorphous phase. Amorphous phases are also referred to as glass phases.In this definition, the glass transition temperature observed withseveral material families is unimportant: to distinguish between acrystalline phase and an amorphous phase, use is generally made of anorder parameter. An order parameter is described for example in:Schmidt, Rainer, Werkstoffverhalten in biologischen Systemen”, (1999),p. 58, doi:10.1007/978-3-642-60074-6. It is noted that it may benecessary to define an order parameter depending on the solid used, sothat no general strategy can be offered for its definition. The value ofthe order parameter is referred to as the degree of order. Completelycrystalline phases are generally described with a degree of order of 1.Amorphous is understood to be a largely disordered phase with a degreeof order less than 0.5, preferably less than 0.2, particular preferablyless than 0.1. A completely amorphous phase has a degree of order of 0.In very many cases, the Landau theory can also be used to define theorder parameter. The aim of the amorphization is to produce a completelyclosed, disordered layer, the surface whereof contributes in furtherprocess steps to the improvement of a bonding process.

There are two basic types of method for producing an amorphization on asubstrate surface.

In a first method, high-energy particles are fired onto the substratesurface, which amorphize a, in particular crystalline, structure. Thesemethods are referred to in the following as amorphization processes.Examples of amorphization processes are ion beam processes and plasmaprocesses.

In a second method according to the invention, materials are depositedon the substrate material. The material and the substrate material arepreferably identical. These processes are referred to subsequently asdeposition processes. Examples of deposition processes are chemicalvapor deposition (CVD) and physical vapor deposition (PVD).

In an amorphization process, the particles that strike the substratesurface have energies between 0.01 eV and 1000 eV, preferably between0.1 eV and 100 eV, still more preferably between 1 eV and 10 eV. Thepenetration depth of the particles into the substrate material isgreater than 0 nm, more preferably greater than 5 nm, still morepreferably greater than 10 nm, most preferably greater than 25 nm, withutmost preference greater than 50 nm.

The thickness of the amorphous layer is less than 50 nm, preferably lessthan 20 nm, particularly preferably less than 10 nm, very particularlypreferably less than 5 nm, in the optimum case less than 2 nm, in theideal case less than 1 nm.

With the method according to the invention, substrates made of the samematerial or with different materials can be bonded together. Thesubstrates preferably comprise functional units, conductor tracks, TSVs,bond islands (pads), etc. In particular, the substrates can also behybrid substrates. A hybrid substrate is understood to mean a substratethat, in particular, comprises a dielectric at the surface, whichsurrounds electrically conductive regions, in particular bond islandsand TSVs. The method according to the invention is also disclosedexplicitly for the bonding of hybrid substrates. Here, the electricallyconductive regions in particular can be amorphized with the aid of themethod according to the invention. The surface of the dielectric is usedfor the prebonding. The amorphized electrically conductive regions makecontact with each other and are then transformed from the amorphousstate into the crystalline state with the aid of the method according tothe invention.

In particular, substrates of different materials can be bonded togetherwith identical amorphous layers. Perfect transitions in the bondinginterface are produced, at most with the exception of dislocations andgrain boundaries. This method enables bonding of different materials, inparticular of semiconductors, and the production of materialtransitions, in particular of semiconductor transitions.

Furthermore, a substrate provided with individual components, inparticular with chips (chip to wafer bond), can be bonded using themethod according to the invention.

Furthermore, chips can be bonded together using the method according tothe invention. In particular, two transparent substrates provided withindividual components can be used as carriers.

The cleanliness of the substrate surfaces reduces theinterstratification of foreign atoms in the bonding interface, whichincreases the performance of the final product, since interferinginfluences are thus reduced.

The cleanliness of the substrate surfaces, in particular of the surfacesto be bonded, should therefore also be characterized. The foreign atomloading of the surfaces to be bonded should comprise, in particular percm², material with in each case less than 50×10¹⁰, preferably in eachcase less than 5×10¹⁰, atoms of the chemical elements Ca, Cr, Co, Cu,Fe, K, Mn, Mo, Na, Ni, Ti and in each case less than 20×10¹¹, preferablyin each case less than 1×10¹¹, atoms of the chemical elements AI, V, Zn.Possible detection methods are

Atomic absorption spectrometry (AAS)

Atomic emission spectrometry (AES)

Energy-dispersive x-ray spectrometry (EDX)

Wavelength-dispersive x-ray spectrometry (WDX)

Radio spectrometry (OES)

Fluoresence methods

-   -   Atomic fluoresence spectroscopy (AFS)    -   X-ray fluorescence analysis (XRF)

For substrates with 200 mm diameter for particles with a measurementsensitivity of the 0.2 microns, the particle loading with foreignparticles is less than 100 particles, preferably less than 75 particles,particularly preferably less than 60 particles.

For substrates with 300 mm diameter for particles with a measurementsensitivity of the 0.2 microns, the particle loading with foreignparticles is less than 200 particles, preferably less than 150particles, particularly preferably less than 115 particles.

A reduced, in particular minimised, particle loading of the surfaces tobe bonded leads to a better prebond, which improves the electronicproperties of the finished product produced according to the invention.

Furthermore, the surface to be bonded can be wetted in a normal cleanroom atmosphere at room temperature with at least one monolayer of waterand monolayers of gases of the air components. In order to remove thesecomponents, heating over 100° C. in a vacuum at 1 bar, preferably atless than 0.5 bar, still more preferably is less than 0.1 mbar, mostpreferably at less than 0.01 mbar, with utmost preference less than0.001 mbar and storage in an evacuated transport container or device isprovided.

A further process parameter of the method according to the invention isthe nature of the radiation. The radiation is absorbed in the amorphouslayers and thus brings about the phase transformation. The wavelengthand the intensity are used as parameters for the selection of theradiation source. Roughly classified, the radiation or its source can beused as a broadband emitter or a monochromatic emitter. A broadbandemitter or the monochromatic emitter, in particular a laser, emits inthe energy range between 1 eV and 10E8 eV, preferably between 1 eV and10E6 eV, still more preferably between 1 eV and 10E4 eV, most preferablybetween 1 eV and 10 eV.

The radiant power of the radiation source lies between 0.01 Watt and10000 Watt, preferably between 0.1 Watt and 1000 Watt, most preferablybetween 1 Watt and 100 Watt.

The radiation can be formed/directed by means of optical elements, suchas, for example, mirrors, lenses, and prisms. The radiation can beformed into a radiation area with a homogeneous radiation distribution.The radiation area is adapted to the substrate stack to be irradiated,or can be generated by a linear source and/or a point-like source with ahigh power and a radiation cross-section of less than 5 mm², preferablyless than 3 mm², particularly preferably less than 1 mm² measured at thepoint of incidence of the radiation.

In particular, locally limited temperatures above 200° C., preferablyabove 400° C., particularly preferably above 600° C., in the optimumcase above 800° C., in the ideal case above 1200° C. can be reached bymeans of radiation in the amorphous phase for the phase transformation.

Depending on the thermal and optical parameters of the amorphous bondinginterface to be transformed, the irradiation time is a control parameterfor the effect of the radiation. The irradiation time, especially in thecase of an unmoved substrate stack, can last less than 30 s, preferablyless than 15 s, particularly preferably less than 1 s, very particularlypreferably less than 100 ms. The effect of the phase transformationdepends on the irradiation time and the degree of its effect on theamorphous phase in the bonding interface, so that time is regarded as anintegral factor.

In particular, the radiation should strike normal (i.e. at an angle of90°), i.e. perpendicular to the bonding interface, wherein a fluctuationof the angle of incidence of less than +/−5 degrees, preferably lessthan +/−3 degrees, particularly preferably less than +/−1 degree ispermissible. In the case of flatter angles of incidence, the reflectioncomponent of the radiation is greater, so that an almost loss-freeenergy input is not guaranteed.

According to the invention, the parameters substrate temperature andatmosphere influence the physical effect of the phase transformation.Energy required that the reaction is split up into a general heat effectby means of conduction temperature control (heating or cooling),convection temperature control and radiation temperature control.Substrate heating increases the general thermal lattice oscillations inthe crystal and of the atoms in the amorphous phase, so that additionalheating to the radiation speeds up the reaction and is accordinglyadvantageous.

Cooling and/or temperature control is of importance for the reactionrates of the phase transformation, since a sufficient nucleation ispromoted by means of temperature control, and the fault locations gaintime to heal the defects. In other words, the thermal gradient betweenthe substrate volume and the heated point in the amorphous phase can bebetter controlled or regulated by the additional variable of the ambientand substrate temperature control. Temperature control courses can thusbe implemented in the optimum manner. The smaller the thermal gradientin the substrate stack is kept, the more stress-free becomes thefinished product. In the temperature control, the differences in thethermal expansion coefficients (both linear and also in the volume) orin the thermal expansions are noted and corrected with computer-assistedcontrol of the temperature course, to an extent such that the producthas a low stress state thermally and mechanically.

The temperature control should diverge from the set temperature in eachcase by less than +/−5 degrees, preferably less than +/−3 degrees, inthe optimum case less than +/−0.1 degrees.

An essential advantage of the method according to the invention is that,as a result of the local heating of the amorphous regions, the thermalexpansion is also limited solely to local regions. The thermal expansionis primarily of relevance when substrates of different materials are tobe bonded together, the thermal expansion coefficients of which greatlydiverge from one another. Table 1 lists several typical semiconductormaterials and their thermal expansion coefficients at room temperature.

Table 1 shows the approximate thermal expansion coefficients α at roomtemperature for different materials which are typically used in thesemiconductor industry. The stated values of the thermal expansioncoefficients are approximate guide values and fluctuate depending on thesource stated in each case. The stated materials all belong to the cubiccrystal system, so that their thermal expansion is isotropic.

TABLE 1 Al Ge Au Ag Cu InP InSb InAs Si AN GaAs GaP GaSb □ in 10⁻⁶ K⁻¹23.1 5.8 14.2 18.9 16.5 4.75 5.37 4.52 2.6 4.5 5.8 4.5 7.75

The difference in the thermal expansion coefficients between twomaterials cannot be eliminated by the method according to the invention,but the thermal expansion can be limited to an extremely small range. Iftwo semiconductor materials with very different thermal expansioncoefficients are bonded together, a thermal expansion will arisedirectly near the amorphous layer, which is transformed with the aid ofthe effect according to the invention into a crystalline layer, but thisthermal expansion rapidly diminishes with increasing distance from thebonding interface. A very marked expansion or stress gradient thusarises. Particularly advantageously, the energy introduced into thebonding interface is even used solely for performing the transformationfrom the amorphous into the crystalline state, without a notable heatingof the bonding interface being carried out. The temperature gradient isthus minimised and therefore also the thermal expansions and stresses.This can preferably take place by means of a pulsed laser operation.

In an embodiment according to the invention, a temperature control ofthe substrate stack above 100° C., preferably above 200° C.,particularly preferably above 300° C. is advantageous, in order that thethermal stresses in the substrate due to the phase transformation arereduced by the higher mobility of the crystalline lattice. Inparticular, fragile substrate materials can be bonded stress-free inprocesses taking place thermodynamically slowly.

In a preferred embodiment, the method according to the invention iscarried out in a vacuum at less than 1 bar, preferably less than 0.1mbar, still more preferably less than 0.01 mbar, most preferably lessthan 0.001 mbar, with utmost preference less than 0.0001 mbar. Inparticular, the bonding interface can be occupied by a monolayer of gasof a defined atmosphere, with which the foreign atoms can be introducedas doping into the amorphous phase.

In another embodiment, an evacuated device can prevent or slow down anagglomeration of fluids (gases or liquids and their vapours). Anoxidation-free layer can thus be produced, i.e. amorphised. Furthermore,a substrate stack can be bonded without interrupting the vacuum.According to the invention, the pre-bonded substrate stack can also bepost-treated thermally without interrupting the vacuum, in particular bymeans of radiation. Accordingly, the bonding interface is at leastreduced, preferably completely eliminated, according to the invention.

The advantage of the embodiment in a vacuum is that even the edge zonesof the substrate stack are bonded without the effects of the atmosphere,so that an improvement in the homogeneity of the bonding interface isbrought about.

According to the invention, the absorption capacity of the substratesurface in the bonding interface for the radiation is greater than theabsorption capacity of the substrate volume.

The substrate volume preferably comprises at least for the most partcrystalline phases, in particular a monocrystalline phase, of thesubstrate material.

Since a radiation intensity at a workpiece is made up of reflection,absorption and transmission, reflection and transmission should be takeninto account. It is of particular importance for the method according tothe invention to limit the reflection at the substrate surfaces andsubstrate stack surfaces to less than 4%, preferably less than 3%,particularly preferably less than 1% of the initial intensity of theradiation source. To achieve this, technical measures can be employedfor the surface finish such as anti-reflection layers and/or moth-eyestructures at the substrate surface lying opposite the bonding side.Furthermore, the coupling of the radiation and the avoidance ofreflections can be promoted by means of liquid and/or liquid filmbetween the radiation source and the substrate surface.

Depending on the wavelength of the radiation source, the transparency ofthe crystalline phases can be subject to a fluctuation of 10%,preferably 5%, particularly preferably 3%, very particularly preferably1%. This is a material parameter, i.e. an adaptation of the radiationsource to the given substrate material is provided.

An exemplary sequence of the method of the invention is described below.

In a first (optional) process step, two substrates, a first substrateand a second substrate, are cleaned and/or pre-treated and/or at leastpartially freed from a natural oxide layer.

In a second process step, the first crystalline, in particularmonocrystalline, substrate is provided with an amorphous layer by meansof a surface treatment. Vapour deposition processes such as CVD orabrasive processes, in particular a plasma treatment or an ion beamtreatment, can be used. The amorphous layer can thus either be depositedor can arise from the surface of the substrate. Optionally, an amorphouslayer can also be produced on both substrates.

In a third (optional) process step, the substrates are aligned with oneanother.

In the fourth process step, the substrates are bonded to form asubstrate stack. A check on the alignment of the pre-bonded substratestack can then optionally take place.

In a fifth process step, the amorphous bonding interface is transformedinto a crystalline phase using radiation according to the invention.After the process step, the amorphous phase quantity is thus less than50%, preferably less than 40%, still more preferably less than 20%, mostpreferably less than 10%, with utmost preference 0%. Correspondinglyafter the process step, the crystalline phase quantity greater than 50%,preferably greater than 60%, still more preferably greater than 80%,most preferably greater than 90%, with utmost preference 100%. Inparticular, a complete transformation of the amorphous phase into acrystalline phase thus takes place. After the process step, thecrystalline phase may have crystal defects such as interstitial and/orsubstitutional atoms, vacancies, edge dislocations, screw dislocationsetc.

In a sixth, optional process step, the finished substrate stack isexamined for successful bonding by means of imaging methods such asmicroscopy for defects and incomplete phase transformation.

Further advantages, features and details of the invention also emergefrom the following description of preferred examples of embodiment andon the basis of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a shows a basic schematic representation of two substrates to bebonded.

FIG. 1b shows a basic schematic representation of two substrates to bebonded following an amorphisation of the surfaces to be bonded.

FIG. 1c shows a basic schematic representation of the alignment of twosubstrates to be bonded.

FIG. 1d shows a substrate stack bonded with a prebond in a basicschematic representation, which has been formed by the two substrates tobe bonded.

FIG. 1e shows the effect according to the invention of radiation on theamorphous layers of a substrate stack as a basic schematicrepresentation, wherein the representation is not true to scale.

FIG. 1f shows the completely heat-treated substrate stack in a basicschematic representation.

FIG. 2 shows a basic schematic representation of three substrates thatcan be bonded using the method according to the invention.

FIG. 3 shows a calculated absorption spectrum for amorphous andcrystalline silicon.

FIG. 4 shows a diagram of the refractive index as a function of theparticle energy for amorphous and crystalline silicon.

FIG. 5a shows schematically a substrate stack with amorphous layers.

FIG. 5b shows schematically a substrate stack during irradiation.

FIG. 5c shows schematically a substrate stack with crystallinestructures.

Identical components or components with the same function are denotedwith the same reference numbers in the figures. The figures are not trueto scale.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1a shows a basic schematic representation, not true to scale, oftwo substrates 1, 2 to be bonded. A first substrate 1 and a secondsubstrate 2 are pretreated in a first optional process step. Thepretreatment can comprise cleaning of the substrates free from chemicaland/or physical impurities, for example from particles. Furthermore, anoxide present can be removed in particular wet-chemically and/ordry-chemically, in particular in a suitable vacuum installation withsubstrate processing. FIG. 1a shows a first process step of an exemplarymethod according to the invention.

For greater clarity, substrate holders, vacuum chamber, grippers, pre-and post-processing devices of the substrate-processing device, togetherwith control, energy and media supply, are not represented in thefigures.

FIG. 1b shows a basic schematic representation, not true to scale, ofsubstrates 1, 2 after an amorphisation of the surfaces to be bonded.First substrate 1 is provided in a device according to the invention(not represented) with a first thin amorphised layer 1 a and secondsubstrate 2 is provided in the device according to the invention (notrepresented) with a second thin amorphised layer 2 a. FIG. 1b is asecond process step of an exemplary method. Alternatively, it would befeasible to dispense with one of the two amorphized layers 1 a, 2 a.

FIG. 1c shows a basic schematic representation, not true to scale, ofthe alignment of substrates 1, 2 to be bonded. First substrate 1 withfirst amorphous layer 1 a is aligned relative to second substrate 2 withsecond amorphous layer 2 a in such a way that amorphous layers 1 a, 2 alie on mutually facing surfaces 1 o, 2 o of amorphous layers 1 o, 2 o.An alignment device is thereby expressly disclosed, but is representedonly symbolically with movement direction arrows P. FIG. 1c is a thirdprocess step of an exemplary method according to the invention.

FIG. 1d shows a substrate stack 3 bonded with a prebond in a basicschematic representation not true to scale, which substrate stack hasarisen from the two substrates 1 and 2 to be bonded. Amorphous layers 1a and 2 a have been joined together by means of the prebond. FIG. 1dshows a fourth process step.

FIG. 1e shows an effect according to the invention of radiation 5 onamorphous layers 1 a and/or 2 a of substrate stack 3, which has beenformed from substrates 1, 2. A radiation source 4 generates radiation 5.The arrows symbolise a relative movement between radiation source 4 andsubstrate stack 3. In particular, radiation 5 can scan over substratestack 3 in a grid-like manner. In another embodiment, the movementtrajectory of the relative movement of a regulation and/or control canbe stored, in particular in a control computer not represented, andimplemented as a prescribed procedure. Optimum path curves for theminimised thermal loading of substrate regions withtemperature-sensitive zones can thus be produced. The modelling and/orcalculation of the trajectory can take place based on simulations suchas FEM or coupled thermal-mechanical modelling. Thus, all the parametersmentioned earlier can be used for establishing and/or adapting theirradiation time, irradiation location and irradiation path andirradiation intensity of the radiation. FIG. 1e shows a fifth processstep.

FIG. 1f shows the heat-treated substrate stack according to theinvention in a basic schematic representation, wherein therepresentation is not true to scale. In the fifth process step carriedout according to the invention, the entire bonding interface or theentire amorphous phase has been transformed into a crystalline phase.The substrate stack is thus permanently bonded inseparably.

FIG. 2 shows a basic schematic representation of three substrates 1, 2,6, which are bonded with the method according to the invention inanother embodiment, wherein the representation is not true to scale. Afirst substrate 1 and a second substrate 2 each receive at least oneamorphous layer 1 a, 2 a. A third substrate 6, with which the substratematerial does not have to be transparent for the radiation, has twoamorphous layers 6 a. After the joining of substrates 1 and 2 tosubstrate 6, a phase transformation according to the invention on bothsides simultaneously or offset in time can produce a substrate stack(not represented) comprising more than two substrates. A substrate stackcomprising three substrates, preferably comprising four substrates,particularly preferably comprising more than five substrates canexpediently be produced using the disclosed method.

The following diagram descriptions show, based on calculated data, theabsorption and refractive-index behaviour of amorphous and crystallinesilicon. The two diagrams are to be regarded as an illustrative examplefor all other materials, which in certain wavelength ranges exhibit thesame behaviour as silicon.

FIG. 3 shows two calculated absorption spectra for amorphous (dottedlines 8) and crystalline (continuous line 9) Si. The diagram showsabsorption index ε as a function of the particle energy, in particularphoton energy in eV. Continuous line 9 represents the absorptionbehaviour of Si in the crystalline phase as a function of the particleenergy. Dotted line 8 represents the absorption behaviour of Si in theamorphous phase as a function of the particle energy. In particle energyrange A between approx. 1.8 eV and 3.0 eV, it can be seen that theamorphous phase has an absorption capacity that is higher by the factor0.2-18 than the crystalline phase. Particles having a particle energybetween 1.8 eV and 3.0 eV are scarcely absorbed by the crystallinephase, but very much so by the amorphous phase.

The disclosed method thus utilises ranges of the spectrum in which theabsorption of the amorphous phase is greater, in particular at least 1.1times greater, preferably 2 times greater, still more preferably morethan 5 times greater, most preferably more than 10 times greater, withutmost preference more than 20 times greater than the absorption of thecrystalline phase.

FIG. 4 shows two calculated refractive index graphs 10, 11 for amorphous(dotted line 10) and crystalline (continuous line 11) Si. The diagramshows refractive index n as a function of particle energy eV, inparticular photon energy. In particle energy range A between approx. 1.8eV and 3.0 eV, it can be seen that refractive indices n of amorphous andcrystalline Si are very similar. All physical processes that are basedsolely on the refractive index are therefore very similar in thisparticle energy range A for amorphous and crystalline silicon. The sameconsiderations apply to crystalline material mixtures with amorphisedphases, insofar as the amorphous phase can be transformed residue-freeinto a crystalline phase.

FIG. 5a shows an enlarged substrate stack 3 (not true to scale) of twosubstrates 1, 2 with corresponding amorphous layers 1 a, 2 a. Individualatoms a1, a2 can be seen, from which the crystalline phases ofsubstrates 1 a, 2 a and the amorphous phases of amorphous layers 1 a, 2a are built up. Atoms a1 of the crystalline phases of substrates 1, 2are ordered, atoms a2 of amorphous phases 1 a, 2 a are disordered.

FIG. 5b shows enlarged substrate stack 3 (not true to scale) ofsubstrates 1, 2 with corresponding amorphous layers 1 a, 2 a, which aretreated with radiation 5. Radiation 5 penetrates essentially unhinderedthrough crystalline substrate 2, but is then absorbed by amorphouslayers 1 a, 2 a. The areas which radiation 5 has already struck arealready crystallised.

FIG. 5c shows enlarged substrate stack 3 (not true to scale) of twosubstrates 1, 2 bonded together almost perfectly without correspondingamorphous layers 1 a, 2 a. A dislocation 7 at the right-hand edge of thefigure can be seen. Represented dislocation 7 is an edge dislocation. Ithas been marked at its lower end with a symbol known to the personskilled in the art, and additionally outlined with a dashed line. Edgedislocation 7 represents an additional row of atoms introduced betweenthe otherwise perfect lattice. The distortion of the lattice atomsarising near dislocation 7 can be seen. Such defects are known to theperson skilled in the art in the field. It is explicitly mentioned thatsuch defects may arise with the method according to the invention, butdo not have to arise.

LIST OF REFERENCE NUMBERS

-   1 First substrate-   1 a First amorphous layer of a first substrate-   1 o Bonding surface of the first layer-   2 Second substrate-   2 a Second amorphous layer of a second substrate-   2 o Bonding surface of the second layer-   3 Substrate stack-   4 Radiation source of the radiation-   5 Radiation-   6 Third substrate-   6 a Amorphous layer of the third substrate-   7 Dislocation-   8, 9 Absorption spectrum-   10, 11 Refractive index graph-   a1, a2 Atoms-   A Particle energy range-   ε Absorption index-   n Refractive index-   P Movement arrows

Having described the invention, the following is claimed:
 1. A methodfor bonding a first substrate with a second substrate, said methodcomprising: producing a first amorphous layer from a hybrid surface ofthe first substrate and/or producing a second amorphous layer from ahybrid surface of the second substrate; forming a hybrid bond betweenthe first substrate and the second substrate at the first amorphouslayer and/or the second amorphous layer to form a substrate stack; andirradiating the first amorphous layer and/or the second amorphous layerwith a radiation having a radiant energy such that at least a portion ofthe first amorphous layer and/or the second amorphous layer is/aretransformed into a crystalline layer or crystalline layers.
 2. Themethod according to claim 1, wherein the first amorphous layer and/orthe second amorphous layer is/are transformed at least partially intothe crystalline layer/crystalline layers.
 3. The method according toclaim 1, wherein the first amorphous layer and/or the second amorphouslayer is produced on at least a portion of a respective bonding surfaceof the first and second substrates.
 4. The method according to claim 1,wherein at least one of the first and second substrates is transparentfor the radiation, wherein at least 50% of the radiant energy of theradiation passes therethrough.
 5. The method according to claim 1,wherein the first amorphous layer and/or the second amorphous layerabsorbs more than 60% of the radiant energy of the radiation.
 6. Themethod according to claim 1, wherein the radiation is laser radiation,wherein the method includes focusing the laser radiation on the firstamorphous layer and/or the second amorphous layer.
 7. The methodaccording to claim 1, wherein the method includes striking the firstamorphous layer and/or the second amorphous layer with the radiation atright angles.
 8. The method according to claim 1, wherein the methodincludes generating the radiation by use of a broadband emitter, whichemits energy in a range between 1 eV and 10E8 eV.
 9. The methodaccording to claim 1, wherein the radiation has a radiant power in arange between 0.01 Watt and 10000 Watt.
 10. The method according toclaim 1, wherein said irradiating of the first amorphous layer and/orthe second amorphous layer with the radiation produces temperatures ofover 200° C.
 11. The method according to claim 1, wherein a time for theirradiating of the first amorphous layer and/or the second amorphouslayer is less than 30 seconds.
 12. The method according to claim 1,wherein the radiation is reflected at respective surfaces of the firstand second substrates and/or surfaces of the substrate stack at lessthan 4% of an output intensity of a radiation source.
 13. The methodaccording to claim 1, wherein the first substrate and/or the secondsubstrate is transparent to the radiation up to at least 95% of anoutput intensity of a radiation source.
 14. The method according toclaim 1, wherein before and/or during said irradiating, at least one ofthe first and second substrates is heated above 100° C.
 15. A device forbonding a first substrate with a second substrate, said devicecomprising: a receiving means for receiving the first and secondsubstrates, the first substrate and/or the second substrate respectivelyhaving a first amorphous layer produced thereon from a hybrid surface ofthe first substrate and/or a second amorphous layer produced thereonfrom a hybrid surface of the second substrate; a bonding device forforming a hybrid bond bonding the first substrate with the secondsubstrate, the bonding device being configured to bond the firstsubstrate with the second substrate at the first amorphous layer and/orthe second amorphous layer to form a substrate stack; and a radiationdevice providing a radiation having a radiant energy, the radiationdevice being configured to irradiate the first amorphous layer and/orthe second amorphous layer with the radiation to at least partiallytransform the first amorphous layer and/or the second amorphous layerinto a crystalline layer or crystalline layers.
 16. A substrate stackcomprising at least a first substrate and a second substrate, said firstand second substrates bonded to each other by the method according toclaim
 1. 17. A substrate stack comprising at least a first substrate anda second substrate, said first and second substrates bonded to eachother by the device according to claim
 15. 18. The method according toclaim 1, wherein the hybrid surface of the first substrate comprises adielectric and electrically conductive regions surrounded by thedielectric, wherein the hybrid surface of the second substrate comprisesa dielectric and electrically conductive regions surrounded by thedielectric, and wherein the hybrid bond is respectively formed betweenhe dielectric and the electrically conductive regions of the hybridsurface of the first substrate and the dielectric and the electricallyconductive regions of the hybrid surface of the second substrate. 19.The device according to claim 15, wherein the hybrid surface of thefirst substrate comprises a dielectric and electrically conductiveregions surrounded by the dielectric, wherein the hybrid surface of thesecond substrate comprises a dielectric and electrically conductiveregions surrounded by the dielectric, and wherein the hybrid bond isrespectively formed between he dielectric and the electricallyconductive regions of the hybrid surface of the first substrate and thedielectric and the electrically conductive regions of the hybrid surfaceof the second substrate.